The present invention relates to dispersed aqueous suspensions. In particular, it relates to dispersed aqueous suspensions of inorganic particulate material and to the production of such suspensions.
Aqueous suspensions of inorganic particulate material, eg. comprising calcium carbonate or kaolin are used widely in a number of applications, eg. to produce pigment or filler containing compositions which may be used in paper manufacture or paper coating or in the production of filled compositions for paints, plastics and the like. Where such suspensions are required in a high solids form it is necessary to disperse the particulate material using a dispersing agent. In many cases, the dispersing agent limits one or more of the properties of the product, eg. its viscosity, its solids concentration or its particle size distribution. The amount of dispersing agent used may need to be limited by a user on cost grounds.
Sodium polyacrylate is the most widely used dispersing agent for inorganic particulate materials such as calcium carbonate. However, in some situations, use of sodium polyacrylate is not ideal. For instance in certain applications requiring high solids concentrations as described hereinafter required dose rates of sodium polyacrylate are too high and therefore too costly, the product viscosities obtained upon dispersion and after a period of time, eg. at least 24 hours, are too high and the suspension solids level has to be reduced to an unacceptably low level to compensate.